1. Field of the Invention
The present invention concerns a friction device for a clutch, in particular for a motor vehicle.
2. Description of the Related Art
A motor vehicle clutch is intended to transmit a torque between the engine flywheel of a motor vehicle and the gearbox input shaft. To this end, the clutch comprises a mechanism, rotationally fixed to the engine flywheel, and a friction device rotationally fixed to the gearbox shaft.
The mechanism comprises a pressure plate and a reaction plate, intended to cooperate with first and second friction linings of the friction device. These friction linings are carried by at least one support, normally of general form of revolution.
The friction device must achieve a compromise between various technical constraints.
On the one hand, it is necessary to limit the weight and inertia of the friction device.
To this end, it is wished to limit the dimensions of the friction linings, for example the thickness and the radial width of these friction linings. It is also wished to avoid the presence of rivets fixing the linings to their support, opting as far as possible for adhesive bonding of these linings to their support.
On the other hand, it is necessary to be able to activate the clutch progressively.
To this end, it is wished to incorporate elastic means, in general an elastomer mass, in the friction device, in order to ensure this progressiveness.
Shearing effects limit the possibilities of arranging the elastomer mass between a lining and its support.
A friction device for a clutch, in particular for a motor vehicle, has therefore been proposed in the prior art, in particular in EP-A-0 419 329, of the type comprising:                first and second friction lining members, coaxial, separated axially, delimited by opposite friction faces, and        means of connecting the two friction lining members fixed together.        
In a friction device of this type, the friction lining members each comprise a support carrying a friction lining. In this case, the elastomer mass is interposed between the first and second supports.
More particularly, each lining support described in EP-A-0 419 329 comprises a peripheral part, annular in shape overall, and a central part connecting with the other lining support. The central parts of the supports are contiguous. The peripheral parts of the supports, separated axially from each other, are connected to the central parts by intermediate parts converging from these peripheral parts towards these central parts.
Because of this, when the friction linings are clamped between the pressure and reaction plates, the peripheral parts of the lining supports deform, diverging towards the intermediate parts of the axially relatively rigid supports. Consequently the separation between the peripheral parts of the lining supports does not vary uniformly radially, when the friction linings are clamped between the pressure and reaction plates.
As a result the friction linings do not cooperate uniformly radially with the pressure and reaction plates, which impairs the performance of the clutch.